Comparison of Natural and Remolded Plastic Clay

Abstract

Tests have been performed on triaxial samples of natural and remolded plastic clay from Winnipeg, Canada, to examine the way natural samples conform with modern conceptual models of soil behavior based largely on remolded samples. The clay contains mixed illites and montmorillonites. In its field condition, it is layered, fissured, overconsolidated, and contains many inclusions. Natural samples were carefully trimmed from blocks of the clay: Remolded samples were reconsolidated from a slurry. All reconsolidation was onedimensional. Normal consolidation and critical state lines for the two sets of samples were parallel, with natural values at higher specific volumes than remolded samples. Post‐yield compressibilities and pore‐water pressures were somewhat higher in natural samples, but strengths and moduli were lower. Yield stresses were similar, but the natural yields were again at higher specific volumes. Geotechnical and geological evidence suggests that the natural clay is cemented. Many fundamental features of critical state soil mechanics were found in the natural samples. Differences were in detail and not in principle.